Portable lantern



FIG. 1 is a side elevation of a portable lantern showing my new design;

FIG. 2 is a front elevation thereof;

FIG. 3 is a rear elevation thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof; and

FIG. 6 is a rear perspective view thereof. 

The ornamental design for a portable lantern, as shown. 